The present invention relates to a novel air conveyor for transporting suspended articles, whereof the aeraulic means enabling jets of air to be generated in the direction of the articles have been perfected so as, in particular, but not exclusively, to make it easier to free articles that have accidentally jammed during transport. Its objects also include a process for freeing articles accidentally jammed during their transport in an air conveyor, a process for slowing down or immobilising articles being transported, and a process for imparting a rhythm to articles being transported. Advantageously, it will find an application in the field of pneumatic conveying of light articles such as, for example empty plastic bottles or flasks which are transported while being suspended via their collars or the like.
To transport light articles and, more especially, plastic bottles or the like, it is known, to date, to use air conveyors equipped with blowing means permitting the creation of a plurality of jets of air orientated towards the articles in their direction of transport.
In the case of articles that can be suspended, such as, for example, plastic bottles comprising a collar in the area of their neck, use is made, more particularly, of air conveyors that are equipped with a guide rail, more commonly referred to as an xe2x80x98under-neck guidexe2x80x99, along which the articles are guided and transported while suspended via their collars, or the like. This type of conveyor is disclosed, for example, in U.S. Pat. No. 4,284,370, or again, in U.S. Pat. No. 5,161,919. It implements a main air duct, commonly referred to as a xe2x80x98plenumxe2x80x99, which extends along the path of the articles, and a blowing channel communicating with the main air duct via blowing slits or the like. The main duct is supplied with air, for example by means of several fans judiciously distributed over its entire length; this air is discharged via the blowing slits in the form of a plurality of air jets enabling the articles to be propelled along the blowing channel. In U.S. Pat. No. 4,284,370, the blowing channel has a rectangular cross-section, and the blowing slits are disposed above the guide rail, which makes it possible to propel the articles by blowing above their collars. In U.S. Pat. No. 5,161,919, the blowing channel has the shape of an inverted V, and the blowing slits are disposed below the guide rail, which enables the articles to be propelled by blowing under their collars.
When plastic bottles, for example, are transported with the aforementioned air conveyors, with the bottles suspended via their collars or the like, they tend, during transport, to oscillate longitudinally forwards and backwards in a vertical plane parallel to their direction of transport. These forward/backward oscillation movements are known to give rise to the forward or backward jamming of the bottles in relation to the guide rail. Forward or backward jamming occurs, for example, when a bottle oscillates forwards or backwards to an excessive degree and becomes jammed in relation to the guide rail in this position, for example by the bottle immediately following it. Jamming is also frequent in the case of an accumulation of bottles. For example, when a bottle comes too quickly into contact with a train of accumulated bottles, it may roll on this bottle, tipping longitudinally backwards. In this case, the following bottle, when it comes into contact with this backward tipping bottle, exerts thereon a pressure which results in the backward tipping bottle riding up and jamming, for instance, in the guide rail. Likewise, when they have accumulated, the bottles are pressed against one another and tend to ride up and jam in the guide rail.
To date, when a bottle jams, a manual intervention becomes necessary in order to free the immobilised bottle and, as a result, the bottles that have accumulated behind said bottle. Such manual interventions take quite a long time and can be prejudicial in terms of productivity, particularly when it is necessary to halt the machine upstream and/or the machine downstream of the conveyor. What is more, with certain types of conveyor, it is not easy to gain access to the bottles being transported, these being, for example, transported at some height or inside a closed conveyor.
The present invention provides a novel air conveyor, one of the main advantages of which is that it enables the articles transported to be freed swiftly, without manual intervention.
The air conveyor according to the invention is known in that it comprises a guide rail on which the articles are to be suspended in order to be transported, and first pneumatic guide means enabling the articles to be propelled along the guide rail in a given direction of transport.
In a manner characteristic of the invention, the air conveyor includes second pneumatic means which are designed to generate, when operated, a plurality of reverse air jets (R) orientated towards the articles in a direction opposite that of their direction of transport.
Thanks to the conveyor according to the invention, it is possible, in particular, in the event of an article jamming, to cause air to be supplied at least to the aeraulic section in which a jam has occurred, the main effect of which is to remove the pressure exerted on each other by the articles that have accumulated and to cause the article that has given rise to the jam to drop back down. Furthermore, when the articles subsequently move off again in the direction of transport, the articles located upstream of the jammed article apply to the latter a complementary mechanical action that facilitates its release.
In the event of forward jamming, it may also be advantageous to cause air to be supplied to one or more aeraulic sections located immediately downstream of the section in which the jam has occurred, so as to cause articles located downstream to return rearwards and to exert a complementary freeing action on the forward jammed article.
In one particular alternative embodiment, the conveyor according to the invention includes means for automatically controlling the supplying of air to each reverse blowing compartment, and means for detecting the jamming of one or more articles in the conveyor, which output detection signals for the control means; the control means are designed for automatically and selectively controlling, on the basis of the detection signals, the supply of air at least to the reverse blowing compartment in the area of which a point of jamming has been detected.
Preferably, the control means are also designed to control automatically, on the basis of the detection signals, the air supply to at least a reverse blowing compartment located immediately downstream of the compartment in the area of which a jam has been detected, so as to cause one or more articles located downstream of the point of jamming to return rearwards.
Another object of the invention is a process for freeing an article, or a plurality of articles, that has/have accidentally jammed while being transported in an air conveyor, in which the articles are transported while suspended.
Characteristically according to the invention, the process consists in generating temporarily, at least over all or some of the articles that are jammed, reverse jets of air that are orientated in the direction opposite the direction of transport of the articles.
According to an additional characteristic of the process of the invention, there are further temporarily generated, downstream of the point of jamming, reverse jets of air that are orientated in the direction opposite that of transport of the articles, so as to cause to return rearwards at least one article located immediately downstream of the point of jamming and to direct it into contact with the jammed article or articles.
A further object of the invention is a process for slowing down or immobilising one or more articles that are suspended and propelled along a guide rail through the action of transport air jets. Characteristically according to the invention, the process consists in generating on the articles reverse jets of air that are orientated in the direction opposite the direction of transport of the articles. In the framework of the invention, the articles can be slowed down or immobilised by using the reverse jets of air at the same time as the transport air jets. In an extreme case, if it is wished to slow down or immobilise the articles very swiftly, it can also be contemplated using, momentarily, only the reverse jets of air, for a time sufficient to obtain the desired slowing down or immobilisation.
Finally, another object of the invention is a process for imparting a rhythm to articles suspended and propelled along a guide rail. This process consists, on one hand, over a first portion of the path of the articles, in slowing down, and possibly immobilising, the article or articles by generating on the articles, in this first portion, reverse jets of air (R) orientated in the direction that is the reverse of the direction of transport of the articles, and, on the other hand, at the exit from the first portion, in accelerating the article or articles through the action of the transport air jets.